How do you use a double concave lens?

1. Introduction to double concave lens

A double concave lens is also called a negative spherical lens. The middle of the lens is thin, the edge is thick, and it is concave, so it is also called a concave lens, which has a divergent effect on light.

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The imaging law of the concave lens is: when the object is a real object, it becomes an upright, reduced virtual image, and the image and the object are on the same side of the lens. The concave lens has a divergent effect on the light, so the lens is also called a divergent lens, a negative spherical lens.

2. Features of biconcave lens:

A double concave lens is concave on both sides and has the same radius of curvature. A double concave lens with a negative focal length is usually used for beam collimation, increasing (decreasing) the focal length or enlarging (shrink) the image.

The double concave lens has a negative focal length and is often used in imaging or beam collimation applications. The coated lens is also widely used in visible light and near-infrared applications.

Conventional lens sizes are: Φ12.7mm, Φ25.4mm, Φ50.8mm, and customized double convex lenses can be produced according to customer project requirements.

3. Double concave lens parameters:

Optional materials: K9, N-BK7, JGS series UV fused silica

Working range: 400 nm-700 nm (other bands can be customized)

Design wavelength: 546.1nm (n=1.519)

Tolerance of focal length: ±2%

Shape tolerance: +0.0/-0.02mm

Thickness tolerance: ±0.02mm

Curved aperture: 3

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Plane flatness (aperture): 1

Surface local aperture: 0.5

Eccentricity: &#;3 arcmin

Surface type: λ/4@632.8nm

Surface finish: National standard three, U.S. military standard 60-40

Clear aperture: >90%

Safe beveling: <0.2X45°

The three light rays traveling into the concave lens shown above travel away from each other. For this reason, concave lens are also called diverging lenses. As a result of this light divergence, concave lenses create only virtual images.

Images in Double Concave Lenses

Every concave lens causes all rays to diverge. Rays that approach the lens parallel to the principal axis refract as if they came from the focal point.

As you can see in the figure above, the light rays hit the lens and refract away from each other. Since none of these rays will intersect, a real image cannot exist. Instead, all images created by a double concave lens are virtual images. Like in all ray diagrams, images can be found using two rays.

The first ray, shown above, begins from the tip of the image and travels to the lens parallel to the principal axis. Within the lens, this ray is refracted away from the principal axis such that the virtual ray (shown as a dotted line) travels back to the focal point. The second ray also leaves from the tip of the object, and travels straight through the center of the lens. The image will be where these two rays intersect - one real and one virtual. Since one ray is a virtual ray, the image will always be virtual, as well as upright and diminished.

Like for convex lenses, the lens equation and magnification equations can be used to calculate image size and distance for double concave lenses. When using the lens equation with a concave lens, however, the focal length must be assigned a negative value.

In the Contact Lens simulation below, the Lens Slider allows you to choose between a converging (convex) contact lens and a diverging (concave) contact lens. Try to view different objects at different distances using these two lenses and determine what is the best shape for the contact lens:

Interactive Element